The new A to F grades released Friday for elementary and middle schools show that the number of A-rated schools fell nearly 39 percent this year, while the number of F-rated schools more than doubled. Grades for high schools won't be released until late this year.

Fourteen schools received F grades in Miami-Dade County, 13 in Broward, and 5 in Palm Beach. No schools received F grades in Monroe County.

Last year, more than 1,200 schools received the A grade that is used by parents and businesses to identify top-rated schools. This year, the preliminary grades resulted in a drop to just 760 schools with A grades.

Top education officials insisted that the changes that kicked in this year — including a raise in required writing test scores — led to the dramatic decline. Other recent changes include incorporating results from new end-of-course exams.

"This year's school grades are indicative of the fact that Florida has continued to raise standards," said Education Commissioner Tony Bennett.

Each year, the state hands out A-to-F grades that are used to reward top schools and sanction those that get failing marks. The system has been in place for more than a decade and was the centerpiece of changes first put in place under then-Gov. Jeb Bush.

Some school superintendents have complained that the current school grades do not reflect true academic performance because of the impact of all the recent changes.

Miami-Dade schools superintendent Alberto Carvalho on Friday tweeted out the drop in grades was "artificial" and that "unreasonable" changes to the formula have undermined the grading system. The school district issued a statement, saying: "Today's announcement of school grades is the result of relentless and unscientific manipulation of accountability rules. Yet, notwithstanding the disproportionately high number of English Language Learners and concentration of disadvantaged students, Miami-Dade County Public Schools experienced far less decline than the State and surrounding Florida districts in the percentage of schools receiving a letter grade of "A", as well as a lower rate of decline in the percentage of "D" and "F" schools. As with other challenges this District has faced, we will approach this one with a well thought out plan which puts the interest and welfare of students first."

That point of view was echoed by the head of the state's teachers union.

Andy Ford, president of the Florida Education Association, argued that the flurry of changes had rendered the grades "meaningless as a comparison of school progress."

"Lower school grades don't reflect a drop in achievement by students," said Ford. "They are the result of numerous changes in the grading system

Bennett has defended the need to include the tougher standards because Florida is transitioning in 2014 to a new set of "common core" standards that could prove even tougher than those in place now.

Bennett, however, said that those schools that received "F'' grades are showing that they are need of help.

Still, the number of F-rated schools could have been higher.

Earlier this month, the State Board of Education voted 4-3 to tweak the formula that allowed as many as 150 schools to avoid getting an F grade. The board adopted a provision recommended by Bennett that prevented any school from dropping more than one letter grade at time.

The decision to change the grading standards was done over the protest of some officials who said the move would confuse parents and mask the true performance of many schools.

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